Contact lenses

ABSTRACT

The invention provides silicone hydrogel contact lenses that exhibit reduced back surface debris and reduced incidence of superior epithelial accurate lesions.

RELATED U.S. APPLICATIONS

This patent application is a continuation of U.S. Ser. No. 13/761,567,filed on Feb. 7, 2013, now U.S. Pat. No. 8,741,981; which is acontinuation of U.S. Ser. No. 12/888,474, filed on Sep. 23, 2010, nowU.S. Pat. No. 8,399,538; which is a continuation of U.S. Ser. No.12/335,081, filed on Dec. 15, 2008, now U.S. Pat. No. 7,825,170, issuedon Nov. 2, 2010; which is a continuation of U.S. Ser. No. 11/029,774,filed on Jan. 5, 2005, now U.S. Pat. No. 7,521,488, issued on Apr. 21,2009, which is a continuation of U.S. Ser. No. 09/973,645, filed on Oct.9, 2001, now U.S. Pat. No. 6,849,671, issued on Feb. 1, 2005; which is acontinuation-in-part of U.S. Ser. No. 09/685,655, filed on Oct. 10,2000, now abandoned; which is a continuation-in-part of U.S. Ser. No.09/957,299, filed on Sep. 20, 2001, now U.S. Pat. No. 6,943,203, issuedon Sep. 13, 2005; which is a continuation-in-part of U.S. Ser. No.09/652,817, filed on Aug. 30, 2000, now abandoned; which is acontinuation-in-part of U.S. Ser. No. 09/532,943, filed on Mar. 22,2000, now abandoned; which is a continuation in part of U.S. Ser. No.09/414,365, filed on Oct. 7, 1999, now abandoned; which is acontinuation-in-part of U.S. Ser. No. 09/033,347, filed on Mar. 2, 1998,now U.S. Pat. No. 5,998,498 issued on Dec. 7, 1999.

FIELD OF THE INVENTION

The present invention relates to contact lenses. In particular, theinvention provides silicone hydrogel contact lenses that exhibit reducedback surface debris and a reduced incidence of superior epithelialaccurate lesions.

BACKGROUND OF THE INVENTION

The use of contact lenses for reasons of cosmetics and for thecorrection of visual acuity is well known. However, use of contactlenses is known to result in the development of either or both superiorepithelial arcuate lesions and superior arcuate staining. Additionally,debris such as mucin balls, cellular debris, lint, dust, bubbles,make-up, or the like (“back-trapped debris”) may become trapped betweenthe back surface of the lens and the eye. These problems have been foundacross the range of conventional soft contact lenses, but are found tobe substantially more prevalent in the high oxygen permeability siliconehydrogel contact lenses introduced into the market within the lastseveral years. Thus, a need exists for a lens that eliminates or reducessuperior arcuate lesions and staining as well as back-trapped debris.

DESCRIPTION OF THE INVENTION AND ITS PREFERRED EMBODIMENTS

The present invention provides silicone hydrogel contact lenses in whichthe formation of superior arcuate staining of grade 2 or higher andsuperior epithelial arcuate lesions along with back-trapped debris issignificantly reduced or substantially eliminated. It is a discovery ofthe invention that by controlling stiffness of the lens at the lens'center, lesion formation and staining may be reduced or eliminated.Additionally, by controlling the lenticular junction stiffness andsurface wettability, back-trapped debris also may be significantlyreduced or eliminated.

In one embodiment, the invention provides a contact lens comprising,consisting essentially of, and consisting of a center stiffness of about1 psi·mm² or less and a lenticular junction stiffness of about 4.4psi·mm² or less, wherein the lens exhibits an advancing contact angle ofless than about 120 degrees. For purposes of the invention, themeasurements necessary for calculating stiffness are taken at roomtemperature and the advancing contact angle is measured usingphysiologically buffered saline. By “center” is meant the center of theoptic zone. By “lenticular junction” is meant the junction of thelenticular zone with the bevel or, for those lenses without a bevel, apoint about 1.2 mm from the lens edge.

The stiffness of a lens at any point may be determined by multiplyingthe lens' Young's modulus with the square of the thickness of the lensat that point. The center stiffness of a lens, thus, may be calculatedby determining the thickness of the lens at the center of the lens'optic zone and multiplying the square of that value by the lens'modulus. The lenticular junction stiffness may be calculated in the samemanner.

It is a discovery of the invention that by maintaining the center andlenticular junction stiffnesses and the advancing contact angle of alens at certain levels, the incidence of SEALs, meaning superior arcuatelesions and superior arcuate staining of about grade 2 or higher, andback-trapped debris may be significantly reduced or substantiallyeliminated. By “grade 2” staining is meant that small aggregates, orgroupings, of corneal epithelial cell loss are visible using sodiumfluorescein. By “significantly reduced” means that SEALs are reduced toan incidence of about 1 percent or less and that less than about 35percent of lens wearers experience no back-trapped debris or only a mildamount, meaning an easily visible amount on slit lamp examination at amagnification of about 16 to about 20×, but which amount is notclinically significant.

Preferably, the center stiffness of lenses of the invention is less thanabout 1 psi·mm², the lenticular junction stiffness is less than about 4psi·mm², and the lens has an advancing contact angle less than about 120degrees. More preferably, the center stiffness of lenses of theinvention is less than about 1 psi·mm², the lenticular junctionstiffness is less than about 4 psi·mm², and the lens has an advancingcontact angle less than about 80 degrees. Most preferably, the centerstiffness of lenses of the invention is less than about 0.5 psi·mm², thelenticular junction stiffness is less than about 4 psi·mm² and theadvancing contact angle is less than about 55 degrees.

The desired stiffnesses for the lenses of the invention may be obtainedby combining materials of any suitable Young's modulus with a suitablelens thickness to obtain the desired stiffness. Additionally, thematerial from which the lens is formed may be such that the lens surfaceexhibits the desired wettability, as exhibited by advancing contactangle. Alternatively, the lens may be coated with a material thatexhibits the desired wettability.

One ordinarily skilled in the art will be capable of determining themodulus and thickness combinations that may be used to obtain thedesired stiffnesses for the lenses of the invention. The lenses of theinvention are soft contact lenses made of silicone hydrogel. Siliconehydrogels useful for forming the lenses of the invention may be made byreacting blends of macromers, monomers, and combinations thereof alongwith additives such as ultraviolet blockers, tints, and polymerizationinitiators. Suitable silicone hydrogel materials include, withoutlimitation, silicone hydrogels made from silicone macromers andhydrophilic monomers. Examples of such silicone macromers include,without limitation, polydimethylsiloxane methacrylated with pendanthydrophilic groups as described in U.S. Pat. Nos. 4,259,467; 4,260,725and 4,261,875; polydimethylsiloxane macromers with polymerizablefunction described in U.S. Pat. Nos. 4,136,250; 4,153,641; 4,189,546;4,182,822; 4,343,927; 4,254,248; 4,355,147; 4,276,402; 4,327,203;4,341,889; 4,486,577; 4,605,712; 4,543,398; 4,661,575; 4,703,097;4,837,289; 4,954,586; 4,954,587; 5,346,946; 5,358,995; 5,387,632;5,451,617; 5,486,579; 5,962,548; 5,981,615; 5,981,675; and 6,039,913;and combinations thereof. They may also be made using polysiloxanemacromers incorporating hydrophilic monomers such as those described inU.S. Pat. Nos. 5,010,141; 5,057,578; 5,314,960; 5,371,147 and 5,336,797;or macromers comprising polydimethylsiloxane blocks and polyether blockssuch as those described in U.S. Pat. Nos. 4,871,785 and 5,034,461. Allof the cited patents are hereby incorporated in their entireties byreference.

Suitable materials also may be made from combinations of oxyperm andionoperm components such as is described in U.S. Pat. Nos. 5,760,100;5,776,999; 5,789,461; 5,807,944; 5,965,631 and 5,958,440. Hydrophilicmonomers may be incorporated into such copolymers, including2-hydroxyethyl methacrylate (“HEMA”), 2-hydroxyethyl acrylate,N,N-dimethylacrylamide (“DMA”), N-vinylpyrrolidone,2-vinyl-4,4′-dimethyl-2-oxazolin-5-one, methacrylic acid, and2-hydroxyethyl methacrylamide. Additional siloxane monomers may beincorporated such as tris(trimethylsiloxy)silylpropyl methacrylate, orthe siloxane monomers described in U.S. Pat. Nos. 5,998,498; 3,808,178;4,139,513; 5,070,215; 5,710,302; 5,714,557 and 5,908,906. They may alsoinclude various toughening agents, tints, UV blockers, and wettingagents. They can be made using diluents such as primary alcohols, or thesecondary or tertiary alcohols described in U.S. Pat. No. 6,020,445. Allof the cited patents are hereby incorporated in their entireties byreference.

In a preferred embodiment, the lenses of the invention are made byreacting a macromer with a reaction mixture that includes silicone basedmonomers and hydrophilic monomers. The macromers may be made bycombining a methacrylate or an acrylate and a silicone in the presenceof a Group Transfer Polymerization (“GTP”) catalyst. These macromerstypically are copolymers of various monomers. They may be formed in sucha way that the monomers come together in distinct blocks, or in agenerally random distribution. These macromers may furthermore belinear, branched, or star shaped. Branched structures are formed forinstance if polymethacrylates, or crosslinkable monomers such as3-(trimethylsiloxy)propyl methacrylate are included in the macromer.

Initiators, reaction conditions, monomers, and catalysts that can beused to make GTP polymers are described in “Group-TransferPolymerization” by O. W. Webster, in Encyclopedia of Polymer Science andEngineering Ed. (John Wiley & Sons) p. 580, 1987. These polymerizationsare conducted under anhydrous conditions. Hydroxyl-functional monomers,like HEMA, may be incorporated as their trimethylsiloxy esters, withhydrolysis to form free hydroxyl groups after polymerization. GTP offersthe ability to assemble macromers with control over molecular weightdistribution and monomer distribution on the chains. This macromer maythen be reacted with a reaction mixture of predominantlypolydimethylsiloxane (preferably, monomethacryloxypropyl terminatedpolydimethylsiloxane (“mPDMS”), and hydrophilic monomers. PreferredmPDMS is of the formula:

wherein b=0 to 100, preferably 8 to 10; R₅₈ is a monovalent groupcontaining a ethylenically unsaturated moiety, preferably a monovalentgroup containing a styryl, vinyl, or methacrylate moiety, morepreferably a methacrylate moiety; each R₅₉ is independently a monovalentalkyl, or aryl group, which may be further substituted with alcohol,amine, ketone, carboxylic acid or ether groups, preferably unsubstitutedmonovalent alkyl or aryl groups, more preferably methyl; and R₆₀ is amonovalent alkyl, or aryl group, which may be further substituted withalcohol, amine, ketone, carboxylic acid or ether groups, preferablyunsubstituted monovalent alkyl or aryl groups, preferably a C₁₋₁₀aliphatic or aromatic group which may include hetero atoms, morepreferably C₃₋₈ alkyl groups, most preferably butyl, particularlysec-butyl group.

Preferred macromer components include mPDMS,3-methacryloxypropyltris(trimethylsiloxy) silane (“TRIS”), methylmethacrylate, HEMA, DMA, methacrylonitrile, ethyl methacrylate, butylmethacrylate, 2-hydroxypropyl-1-methacrylate, 2-hydroxyethylmethacrylamide and methacrylic acid. It is even more preferred that themacromer is made from a reaction mixture of HEMA, methyl methacrylate,TRIS, and mPDMS. It is most preferred that macromer is made from areaction mixture comprising, consisting essentially of, or consisting ofabout 19.1 moles of HEMA, about 2.8 moles of methyl methacrylate, about7.9 moles of TRIS, and about 3.3 moles of mono-methacryloxypropylterminated mono-butyl terminated polydimethylsiloxane, and is completedby reacting the aforementioned material with about 2.0 moles per mole of3-isopropenyl-ω,ω-dimethylbenzyl isocyanate using dibutyltin dilaurateas a catalyst.

The reactive components of silicone hydrogels typically are acombination of hydrophobic silicone with very hydrophilic components andthese components are often immiscible due to their differences inpolarity. Thus, it is particularly advantageous to incorporate acombination of hydrophobic silicone monomers with hydrophilic monomers,especially those with hydroxyl groups, into the macromer. The macromercan then serve to compatibilize the additional silicone and hydrophilicmonomers that are incorporated in the final reaction mixture. Theseblends typically also contain diluents to further compatibilize andsolubilize all components. Preferably, the silicone based hydrogels aremade by reacting the following monomer mix: macromer; an Si₈₋₁₀monomethacryloxy terminated polydimethyl siloxane; and hydrophilicmonomers together with minor amounts of additives and photoinitiators.It is more preferred that the hydrogels are made by reacting macromer;an Si₈₋₁₀ monomethacryloxy terminated polydimethyl siloxane; TRIS; DMA;HEMA; and tetraethyleneglycol dimethacrylate (“TEGDMA”). It is mostpreferred that the hydrogels are made from the reaction of (all amountsare calculated as weight percent of the total weight of the combination)macromer (about 18%); an Si₈₋₁₀ monomethacryloxy terminated polydimethylsiloxane (about 28%); TRIS (about 14%); DMA (about 26%); HEMA (about5%); TEGDMA (about 1%), polyvinylpyrrolidone (“PVP”) (about 5%); withthe balance comprising minor amounts of additives and photoinitiators,and that the reaction is conducted in the presence of 20% wtdimethyl-3-octanol diluent.

The desired wettability and, thus, the desired advancing contact angle,for the lenses' surfaces may be obtained by any convenient method suchas by application of a suitable hydrophilic coating. The coatings may beapplied by any convenient method. Preferred hydrophilic coatingsinclude, without limitation, poly(acrylic acid), poly(methacrylic acid),poly(maleic acid), poly(itaconic acid), poly(acrylamide),poly(dimethacrylamide), block or random copolymers of (meth)acrylicacid, acrylic acid, maleic acid, itaconic acid with any reactive vinylmonomer, carboxymethylated polymers, such as carboxymethylcellulose,dextran, polyvinyl alcohol, polyethylene oxide, poly(HEMA),polysulfonates, polysulfates, polylactam, polyglycolic acid, polyamines,and the like, and mixtures thereof. More preferably, the coating ispoly(acrylic acid), poly(methacrylic acid), poly(dimeth)acrylamide,poly(acrylamide), or poly(HEMA). Most preferably, poly(acrylic acid),poly(acrylamide), or poly(HEMA) is used.

In a preferred coating method, the lens surface to be coated iscontacted with the hydrophilic coating and at least one coupling agentin any convenient manner. Useful coupling agents include, withoutlimitation, dehydrating agents such as carbodiimides, acid halides ofinorganic or organic acids, isocyanides, and the like, and combinationsthereof. Examples of suitable coupling agents include, withoutlimitation, carbodiimides, N,N′-carbonyldiimidazole, phosphorylchloride, titanium tetrachloride, sulfuryl chloride fluoride,chlorosulfonyl isocyanate, phosphorus iodide, pyridinium salts oftributyl amine, phenyl dichlorophosphate, polyphosphate ester,chlorosilanes, and the like as well as mixtures of tributyl phosphorusand phenyl isocyanate, alkyl chloroformates and triethyl amine,2-chloro-1,3,5-trinitrobenzene and pyridine, methyl sulfuryl chlorideand diethyl amine, and triphenylphosphine, carbon tetrachloride andtriethyl amine Preferred coupling agents are carbodiimides. Morepreferred are 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide anddicyclohexyl carbodiimide.

The lens may be placed in a solution of coating and solvent into whichthe coupling agent is added. As an alternative, and preferably, the lenssurface may first be contacted with one of the coupling agent or coatingand then contacted with the other. Most preferably, the surface is firstcontacted by any convenient method with the coupling agent for a periodof about 0.5 to about 60 minutes, preferably for about 1 to about 30minutes. Subsequently, the surface is contacted with the hydrophilicpolymer solution for a period of about 1 to about 1000 minutes,preferably about 5 to about 200 minutes. Suitable solvents for use arethose that are capable of solubilizing both the hydrophilic polymer andthe coupling agent. Preferably, the coating process is carried out in awater or aqueous solution, which solution preferably contains buffersand salts. The carbodiimide1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (“EDC”) is effective inaqueous solutions and, thus, is a most preferred coupling agent.

A coupling effective amount of the coupling agent is used which amountis sufficient to couple the hydrophilic coating to the lens surface. Theprecise amount of coupling agent used will depend on the lens surfacechemistry as well as the coating and coupling agent selected. Generally,about 0.01 to about 10 weight percent, preferably about 0.01 to about5.0, more preferably, about 0.01 to about 1 weight percent of thecoating solution is used. By coating solution is meant the coating withone or more of the solvent, coupling agent, and, optionally, a buffer.Typically, the amount of coating solution used per lens will be about0.1 to about 100 g, preferably about 0.5 to about 50 grams, morepreferably about 1 to about 10 g per lens. A coating effective amount ofthe hydrophilic coating is used meaning an amount sufficient to coat thesurface to the desired degree. Generally, the amount of polymer used isabout 0.001 to about 100, preferably about 0.01 to about 50, morepreferably, about 0.01 to about 10 weight percent of the coatingsolution.

Following contacting, the surface may be washed with water or bufferedsaline solution to remove unreacted polymer, coupling agent, solvent,and byproducts. Optionally, the coated surface may be heated in water toextract residual coating, coupling agent, and byproducts and to ensurethe break down of any coupling agent—stabilizer complexes that may haveformed.

Alternatively, the desired wettability may be obtained using an internalwetting agent in the lens formulation, which wetting agent isnon-fugitive by means of entanglement or copolymerization into thecrosslinked lens polymer network and has a weight average molecularweight of about 100,000 to 500,000 daltons, preferably about 300,000 toabout 500,000 daltons. Suitable wetting agents include, withoutlimitation, polyamides, polylactams, polyimides, polylactones, andcombinations thereof. Preferable wetting agents are PVP, polyacrylamide,polydimethacrylamide, polyoxazolone, imidazolones, hydrolyzed andnon-hydrolized polyvinylacetate, and combinations thereof. Morepreferably, PVP is used.

The lenses of the invention may be made using any known process forcontact lens production. Preferably, the lenses are made by photocuringthe lens composition and, if desired, applying a coating to the curedlens. Various processes are known for molding the reaction mixture inthe production of contact lenses, including spincasting and staticcasting. The preferred method for producing contact lenses of thisinvention is by the direct molding of the silicone hydrogels, which iseconomical, and enables precise control over the final shape of thehydrated lens. For this method, the reaction mixture is placed in a moldhaving the shape of the final desired silicone hydrogel, i.e.water-swollen polymer, and the reaction mixture is subjected toconditions whereby the monomers polymerize, to thereby produce a polymerin the approximate shape of the final desired product. The conditionsfor such polymerization are well known in the art. The polymer mixtureoptionally may be treated with a solvent and then water, producing asilicone hydrogel having a final size and shape similar to the size andshape of the original molded polymer article. This method can be used toform contact lenses and is further described in U.S. Pat. Nos.4,495,313, 4,680,336, 4,889,664 and 5,039,459 incorporated herein byreference in their entireties.

The invention will be clarified by consideration of the following,non-limiting examples.

EXAMPLES Macromer Preparation

To a dry container housed in a dry box under nitrogen at ambienttemperature was added 30.0 g (0.277 mol) ofbis(dimethylamino)methylsilane, a solution of 13.75 ml of a 1M solutionof tetrabutyl ammonium-m-chlorobenzoate (“TBACB”) (386.0 g TBACB in 1000ml dry THF), 61.39 g (0.578 mol) of p-xylene, 154.28 g (1.541 mol)methyl methacrylate (1.4 equivalents relative to initiator), 1892.13(9.352 mol) 2-(trimethylsiloxy)ethyl methacrylate (8.5 equivalentsrelative to initiator) and 4399.78 g (61.01 mol) of THF. To a dry,three-necked, round-bottomed flask equipped with a thermocouple andcondenser, all connected to a nitrogen source, was charged the abovemixture prepared in the dry box.

The reaction mixture was cooled to 15° C. while stirring and purgingwith nitrogen. After the solution reaches 15° C., 191.75 g (1.100 mol)of 1-trimethylsiloxy-1-methoxy-2-methylpropene (1 equivalent) wasinjected into the reaction vessel. The reaction was allowed to exothermto approximately 62° C. and then 30 ml of a 0.40 M solution of 154.4 gTBACB in 11 ml of dry THF was metered in throughout the remainder of thereaction. After the temperature of reaction reached 30° C. and themetering began, a solution of 467.56 g (2.311 mol)2-(trimethylsiloxy)ethyl methacrylate (2.1 equivalents relative to theinitiator), 3636.6. g (3.463 mol) n-butylmonomethacryloxypropyl-polydimethylsiloxane (3.2 equivalents relative tothe initiator), 3673.84 g (8.689 mol) TRIS (7.9 equivalents relative tothe initiator) and 20.0 g bis(dimethylamino)methylsilane was added.

The mixture was allowed to exotherm to approximately 38-42° C. and thenallowed to cool to 30° C. At that time, a solution of 10.0 g (0.076 mol)bis(dimethylamino)methylsilane, 154.26 g (1.541 mol) methyl methacrylate(1.4 equivalents relative to the initiator) and 1892.13 g (9.352 mol)2-trimethylsiloxy)ethyl methacrylate (8.5 equivalents relative to theinitiator) was added and the mixture again allowed to exotherm toapproximately 40° C. The reaction temperature dropped to approximately30° C. and 2 gallons of tetrahydrofuran (“THF”) were added to decreasethe viscosity. A solution of 439.69 g water, 740.6 g methanol and 8.8 g(0.068 mol) dichloroacetic acid was added and the mixture refluxed for4.5 hours to de-block the protecting groups on the HEMA. Volatiles werethen removed and toluene added to aid in removal of the water until avapor temperature of 110° C. was reached.

The reaction flask was maintained at approximately 110° C. and asolution of 443 g (2.201 mol) dimethyl meta-isopropenyl benzylisocyanate (“TMI”) and 5.7 g (0.010 mol) dibutyltin dilaurate wereadded. The mixture was reacted until the isocyanate peak was gone by IR.The toluene was evaporated under reduced pressure to yield an off-white,anhydrous, waxy reactive monomer. The macromer was placed into acetoneat a weight basis of approximately 2:1 acetone to macromer. After 24hrs, water was added to precipitate out the macromer and the macromerwas filtered and dried using a vacuum oven between 45 and 60° C. for20-30 hrs.

Lens Formation

For Lenses 1 through 4, 7 and 10 through 13 of the Table, siliconehydrogels lenses were made using the above-described macromer andmonomer mixtures specified in the Table according to the followingprocedure. All amounts are calculated as weight percent of the totalweight of the combination with the balance of the mixture being minoramounts of additives. Contact lenses were formed by adding about 0.10 gof the monomer mix to the cavity of an eight cavity lens mold of thetype described in U.S. Pat. No. 4,640,489, incorporated herein in itsentirety by reference, and curing for 1200 sec. Polymerization occurredunder a nitrogen purge and was photoinitiated with UV light or withvisible light generated with a Philips TL 20W/03T fluorescent, and anappropriate initiator such as CGI 1850. After curing, the molds wereopened, and the lenses were released into a 1:1 blend of water andethanol, then leached in ethanol or isopropanol/deionied water to removeany residual monomers and diluent. Finally the lenses were equilibratedin physiological borate-buffered saline.

Lenses 8 and 14 were made as follows. 12.5 g KOH were added to 350 g of20 mole propoxylate of methyl glucose available from AmericolCorporation as GLUCAM™ P-20 in a high temperature reactor. The mixturewas heated to 105° C., stirred for 10 min. with nitrogen sparging, andthen pulling vacuum. After repeating the sparge/vacuum two more times,the pressure was allowed to rise to 10 psi and temperature was increasedto 125° C. 1922 g propylene oxide were added gradually over 7 hourswhile maintaining a pressure of 30-40 psi and temperature of 135° C.After continuing agitation overnight, 947 g ethylene oxide were addedfollowing a similar procedure. The product was neutralized with 9.1 gphosphoric acid and filtered with dicalite to give a slightly hazyliquid with a hydroxyl number if 28.3 mg KOH/g.

To a solution of 200 g of this product was added 21.0 g triethylamineand 342 mg N,N-dimethylaminopyridine in 600 g dry ethylene glycoldimethyl at 40° C. 32.1 g of methacrylic anhydride in 250 g ethyleneglycol dimethyl ether were added drop-wise to the reaction flask over a7-8 hour period. The reaction was continued at 40° C. for 7 days.

The reaction temperature was decreased to 25° C. and 100 ml deionizedwater were added. The pH of the reaction mixture was adjusted to 7.0using a 5% aqueous hydrochloric acid solution. 600 g of AMBERLITE™ IRA96 were added and the mixture stirred for 1½ hours. The AMEBRLITE™ IRA96 was removed by filtration and the mixture volatilized at 30-35° C.under reduced pressure.

Approximately 1 L chloroform was added and the resulting liquid waswashed with an equal volume of 5% aqueous solution of sodiumbicarbonate×2 and with saturated sodium chloride×1. The organic layerwas passed through a 400 g silica bed. 100 mg of 4-methoxyphenol wereadded and the chloroform removed under pressure to remove residualchloroform and yield a macromer.

A blend was made of 11.2% of the macromer, 40% TRIS, 28% DMA, 0.8%DAROCUR™ 1173 (2-hydroxy-2-methyl-1-phenyl-propan-1-one) and 20%1-hexanol. The blend was cured in contact lens molds by exposure to UVlight for 30 min. The molds were opened and the lenses released into ablend of isopropanol and water, rinsed with isopropanol, and placed intoborate buffered saline.

The lenses were dried overnight in a clean room. The dried lenses werecoated with diethylene glycol vinyl ether using pulsed plasma vapordeposition. The lenses were placed onto a tray concave side up, the traywas placed into a plasma chamber, and the lenses were subjected to 2min. continuous wave argon plasma at 100 w and 200 m torr. Following theargon plasma, the lenses were subjected to a diethylene glycol vinylether pulsed plasma for 15 min. at 100 W and 70 m torr with a plasmaon/off cycle of 10/200 msec. The lenses then were flipped so that theconvex side faced upwardly and the process was repeated. The lenses werepulled from the chamber and re-hydrated in borate buffered salinepacking solution.

The following lenses were used:

Lens 1—daily wear lenses coated with poly(acrylic acid) made of 17.98 wtpercent macromer, 21.00 wt percent TRIS, 25.50 wt percent DMA, 21.00 wtpercent mPDMS, 2.00 wt percent NORBLOC(2-(2′-hydroxy-5-methacrylyloxyethylphenyl-2H-benzotriazole), 1.00 wtpercent CGI 1850 ((1:1 [wt] blend of 1-hydroxycyclohexyl phenyl) ketoneand bis(2,6-dimethoxybenzoyl)-2,4,-4-trimethylpentyl phosphine oxide),1.50 wt percent TEGDMA, 5.00 wt percent HEMA, 0.02 wt percent Blue HEMA(the reaction product of reactive blue number 4 and HEMA, as describedin Example 4 of U.S. Pat. No. 5,944,853), 5.00 wt percent PVP, 20 wtpercent D30 diluent.

Lens 2—daily wear coated with poly(acrylic acid) and made of 17.98 wtpercent Macromer, 14.00 wt percent TRIS, 26 wt percent DMA, 28.00 wtpercent mPDMS, 2.00 wt percent NORBLOC, 1.00 wt percent CGI 1850, 1.00wt percent TEGDMA, 5.00 wt percent HEMA, 0.02 wt percent Blue HEMA, 5.00wt percent PVP, 20 wt percent D30 diluent.

Lens 3—daily wear lenses made of the material of Lens 2.

Lens 4—daily wear, polyacrylamide coated using EDC lenses, made of thesame material as Lens 2.

Lens 5—FOCUS® NIGHT & DAY daily wear lens, plasma coated, made oflotrafilcon A.

Lens 6—PUREVISION® daily wear, plasma coated, made of balafilcon A.

Lens 7—daily wear, poly(acrylic acid) coated using EDC lenses made ofthe same material as Lens 2.

Lens 8—daily wear, plasma coated lenses made with GLUCAM™ P-20.

Lens 9—extended wear, PUREVISION® plasma coated, lenses made ofbalafilcon A.

Lens 10—extended wear, poly(acrylic acid) coated using EDC lenses madeof the same material as Lens 2.

Lens 11—extended wear, poly(acrylic acid) coated using EDC lenses madeof the same material as Lens 2.

Lens 12—extended wear, polyacrylamide coated lenses made as the samematerial as Lens 2.

Lens 13—extended wear, uncoated lenses made of the material samematerial as Lens 2.

Lens 14—extended wear, plasma coated lenses made with GLUCAM™ P-20.

Clinical testing of lenses of each of these materials was carried out assingle masked, contra-lateral studies according to the followingprocedure. Test subjects were soft contact lens wearers. The subjectswere fitted with the study lenses and sent home with the lenses withinstructions to wear the lenses either for daily or extended wear. Allsubjects in the daily wear lens studies were given an approvedmulti-purpose lens care solution and instructions for cleaning, rinsing,and disinfecting of the lenses.

Lenses 1 through 4 and 7 through 14 were worn for 1 week. Lenses 5 and 6were worn for 2 weeks, but the measurements in the Table are based on 1week wear. For the daily wear lenses, subjects inserted the lenses inthe morning and removed them at night followed by storage in theapproved lens care solution overnight. For extended wear lenses, thelenses were inserted on day 1 and removed on day 7. All subjects werepermitted to remove their lenses when necessary for rinsing withpreservative-free saline.

After 7 days, the subjects' eyes were then examined for visual acuity,back-trapped debris, corneal and conjunctival staining, and conjunctivalhyperemia. SEALs incidence was measured by examining the subjects' eyesfor grade 4, arc-shaped staining of the cornea accompanied, orunaccompanied, by epithelial splitting, corneal infiltrates, or both.

Superior epithelial arcuate lesions were defined as grade 4-typearc-shaped staining in the superior quadrant of the cornea, whichstaining also may be accompanied by epithelial splitting, cornealinfiltrates, or both. A suspected lesion, or superior arcuate staining,was defined as grade 2 or 3-type arc-shaped staining in the superiorquadrant of the cornea. The rates stated in the Table are the percentageof patients who develop either a lesion or a suspected lesion during thecourse of the study. Corneal staining was performed using a slit lampbiomicroscope with a cobalt blue illumination source, a 312 wrattenfilter and 1% minims sodium fluorescein. The slit lamp beam was set to aheight of 6 mm and a width of 2 mm with a magnification of 16-20×. Thefollowing scale was utilized to determine the type and grade of thecorneal staining: grade 1, individual or isolated cell loss; grade 2,small aggregates of cells; grade 3, coalesced aggregates; and grade 4,cell loss in excess of 1 mm.

Back-trapped debris was measured using a slit lamp with a beam set to a2 mm width and a 6 mm height with a magnification between 16 and 20×.Back-trapped debris appeared in a variety of forms including, withoutlimitation, as flaked white or off-color spots, or opaque or off-whitespherical spots or streaks in the post-tear film. Back-trapped debriswas differentiated from deposits that moved with the lens. On the tableis shown the percentage of lens wearers experiencing no back-trappeddebris or a slight amount.

The dynamic contact angle was measured as follows. Five samples of eachlens type were prepared by cutting out a center strip approximately 5 mmin width and equilibrating the strip in borate buffered saline solutionfor more than 30 min. Dynamic contact angles of the strips weredetermined using a Cahn DCA-315 micro-balance. Each sample was cycled×4in borate buffered saline and the cycles were averaged to obtain theadvancing and receding contact angles for each lens. The contact anglesof the 5 lenses were then averaged to obtain the mean contact angle forthe set.

Tensile modulus was determined as follows. Twelve lenses were cut intodog-bone shapes and the modulus and elongation to break were measuredusing and INSTRON™ Model 1122 tensile tester. The lenses were hydrated,using their original packing solution, immediately prior to undergoingtesting. The tensile modulus of the 12 lenses were averaged to obtainthe mean modulus for the set. The results are shown below on the Table.

TABLE 1 Subjects Subjects Center LJ Back- in in Stiffness Stiffnesstrapped Contact Clinical Clinical Mod. CT^(A) (psi · (psi- Seal DebrisAngle SEAL BTD Lens (psi) (μm) mm²) LJT^(B) mm²) (%) (“BTD”) (deg.)Study Study 1 110 124 1.69 224 5.52 10  0.89 57 20 22 2 88 90 0.71 2224.34 0 1.00 <55 22 22 3 89.5 70 0.44 215 4.14 0 .90 70 20 20 4 87.3 770.52 215 4.04 0 1.00 <55 30 30 5 238 80 1.52 165 6.48  5^(C) 0.72 67 —23 6 155 90 1.26 93 1.33  5^(C) 1.00 117 — 25 7 88 170 2.54 238 4.98 33 0.86 <55 30 30 8 73 68 0.34 210 3.22 0 1.0 81 29 29 9 155 90 1.26 92.51.33 11  0.72 117 18 18 10 88 90 0.71 222 4.34 0 0.83 <55 18 18 11 81 700.40 215 3.74 0 0.80 <55 25 25 12 87 70 0.43 215 4.04 0 0.75 <55 28 2813 86 70 0.42 215 3.95 0 0.35 70 20 30 14 73 68 0.34 210 3.22 0 1.0 8136 36 ^(A)Center thickness. ^(B)Lenticular junction thickness.^(C)Sweeney, D. B., “Comparative Incidence of SEALs With High Dk SoftLenses”, Physiology and Pathophysiology, page 17 (August 1999).

The results shown on Table 1 demonstrate that lenses of the inventionexhibit low or no SEALs and minimal back-trapped debris formation.Lenses 1, 5-7 and 9 are comparative examples showing that when lensesfail to meet the thickness and wettability criteria, SEALs andback-trapped debris are present in unacceptable levels.

What is claimed is:
 1. A silicone contact lens comprising a centerstiffness of about 1 psi·mm² or less, a crosslinked lens polymer networkcomprising at least one wetting agent copolymerized therein and anadvancing contact angle is less than about 80 degrees.
 2. The contactlens of claim 1, wherein lenticular junction stiffness is about 4psi·mm² or less.
 3. The lens of claim 1, wherein a center stiffness ofabout 0.5 psi·mm² or less and a lenticular junction stiffness of about 4psi·mm² or less.
 4. The contact lens of claim 1, 2, or 3, wherein theadvancing contact angle is less than about 80 degrees.
 5. The contactlens of claim 1, 2 or 3, wherein the advancing contact angle is lessthan about 55 degrees.
 6. The lens of claim 4, wherein the internalwetting agent is selected from the group consisting of polyamides,polylactams, polyimides, polylactones, and combinations thereof.
 7. Thelens of claim 1 wherein said contact lens is formed from a polymerreaction mixture comprising at least one monomethacryloxypropylterminated polydimethylsiloxane of the formula:

wherein b is an integer from 0 to 100; R₅₈ is a monovalent groupcontaining a ethylenically unsaturated moiety; each R₅₉ is independentlya monovalent alkyl, or aryl group, which may be further substituted withalcohol, amine, ketone, carboxylic acid or ether groups; and R₆₀ is amonovalent alkyl, or aryl group, which may be further substituted withalcohol, amine, ketone, carboxylic acid or ether groups.
 8. The lens ofclaim 7 wherein R₅₈ comprises a methacrylate moiety; each R₅₉ is methyl;and R₆₀ is selected from the group consisting of C₁₋₁₀ aliphatic oraromatic group which may include hetero atoms.
 9. The lens of claim 8wherein R₆₀ is selected from the group consisting of C₃₋₈ alkyl groups.10. The lens of claim 9 wherein b is an integer from 8 to 10.